Gas turbine compressors are used in a variety of industrial applications. For instance, gas turbine compressors may be installed in aircrafts for proving aircraft propulsion. They may even be utilized as stationary power generators and/or stationary mechanical drive. Regardless of the application, gas turbine compressors all consume very large quantities of air. In operation, a gas turbine compressor first compresses air, mixes the compressed air with fuel, and then burns the fuel-air mixture to create expanding gas. This expanding gas in turn drives the turbine compressor and produces torque. The resultant torque may be used, for example, to drive propulsion fans, electric generators, and/or other devices such as mechanical pumps.
In many turbine compressor applications, including those discussed above (with the exception of an aircraft propulsion application), air inlet filtering is employed in an effort to prevent contaminants from entering and hampering the turbines' operations. As can be appreciated by those in the art, however, this type of filtering does not altogether prevent small concentrations of contaminates from entering and adhering themselves to turbine compressor blades. These small concentrations eventually accumulate on the compressor blades and decrease the effectiveness of the blades in a manner that reduces total air flow and total produced power from the gas turbine.
One manner of preventing degradation and of reversing the surface modifying or fouling effects of contaminants is through proper and routine compressor cleaning. Routine cleaning of compressors helps maintain turbine engine performance, emissions performance, and intended air flow at their best. Maintaining the intended air flow also assists in maintaining an optimal fuel to air mixture, which further improves the performance and life of compressors.
Existing methods and equipment utilized in cleaning aero-engine compressors are described in various patents or applications, all of which are incorporated herein by reference. For example, one such compressor cleaning system is disclosed in International Publication No. WO 05077554, entitled “Method and Apparatus for Cleaning Turbofan Gas Turbine Engines” and its corresponding United States Published Patent Application No 2006/0048796. Disclosed therein is a cleaning device comprising a plurality of nozzles arranged on a manifold, which manifold is releasibly mounted on the air inlet of the engine, and where the nozzles are arranged to atomize and direct cleaning liquid in the air stream up-stream of a fan of the engine.
The device as disclosed in WO 05077554 comprises a first nozzle arranged at a first position relative a centre line of the engine such that the cleaning liquid emanated from the first nozzle impinges the surfaces of the blades substantially on the pressure side of the fan; a second nozzle arranged at a second position relative the centre line of the engine such that the cleaning liquid emanated from the second nozzle passes between fan blades and impinges the surfaces of the blades substantially on the suction side of the low pressure compressor; and a third nozzle arranged at a third position relative the centre line of the engine such that the cleaning liquid emanated from the third nozzle passes substantially between the blades and enters an inlet of the core engine. A specific design washing configuration, including flow rate, atomized droplet size, is prepared for each specific engine such that atomization and nozzle position are optimized to achieve effective cleaning.
Thus, the invention disclosed in WO 05077554 is based on the insight that the engine geometry and properties of the fouling of different components of the engine have different properties and therefore, require different approaches for the cleaning. As an example, the fouling of a core compressor may have different properties than fouling found on the blades of a fan. One possible reason for this discrepancy in fouling properties may include, for example, that the temperature is much higher at the compressor than at the blades of a fan. The high temperature at the compressor results in fouling particles becoming “baked” onto the compressor's surface, thereby making removal of such fouling extremely difficult. At the fan blades, however, the temperature is much lower. As a result, the fouling at the fan does not become baked, making it much easier to clean fan fouling.
Another aspect of the cleaning aero-engine compressors includes the proper collection and disposal of washing liquids used to clean the compressors, and any contaminants removed from the aero-engines during a cleaning process. Due to environmental concerns, used washing liquids may be purified and recycled, such as is described in International Publication No. WO 05120953, entitled “System and Devices for Collecting and Treating Waste Water from Engine Washing”. Disclosed therein is an aero-engine washing device having a collector arranged at its rear arrangement for collecting used washing liquids. Waste wash liquid emanating from an engine is collected by this collecting device at the rear of the engine.
The system described in International Publication No. WO 05120953 may be made mobile by the introduction of a mobile vehicle. In operation, the washing device may be mounted or positioned onto a hand-towed cart, a motor driven cart, a motor vehicle (e.g., small truck), or the like.
Another example of a waste water collecting device is described in International Publication No. WO 05121509, titled “System and Devices for Collecting and Treating Waste Water from Engine Washing”, and its corresponding United States Published Patent Application No. 2006/0081521. As disclosed therein, collected waste liquid is pumped into a tank where released fouling material is separated from the collected liquid by an appropriate waste water treatment process. The treated water is then used for either washing additional engines or is alternatively dumped into a sewer.
The above mentioned systems and methods for cleaning engines and/or collecting and recycling used washing liquids provide very versatile and effective cleaning methods that can be arranged on a mobile unit. These systems and methods, however, are not truly fully integrated or self-contained. In other words, each of the above systems requires, to some extent, some form of external resource.
To illustrate, conventional aero-engine (and/or mechanical drive unit) cleaning systems typically require an external source of clean water, (preferably less than five (5) parts-per-million (ppm) total dissolved solids, a power source for heating cleaning solution and driving a cleaning process, a pump to deliver water/wash fluids to the aero-engine, a manifold to direct and atomize the water/wash fluids, and a collection system for capturing used wash fluids (i.e., cleaning effluent) to prevent environmental release. Stationary gas turbine compressor cleaning systems, for example, are typically positioned on a permanently placed skid and require siting of external resources such as a clean water source, power to heat and deliver cleaning solution, a pump system to deliver the cleaning solution, and permanently mounted nozzles within the gas turbine inlet to properly direct the cleaning solution.
Due to the high costs and limited annual use of such a cleaning system, however, some gas turbine operations, (e.g., typically peaking or portable rental units), do not site a permanently mounted skid and forgo routine cleaning of their gas turbines. As can be appreciated by those in the art, forgoing routine turbine cleaning can reduce machine output by up to one-percent (1%) per accumulated month of operation, depending on climate and site. This type of loss to efficiency typically results in higher than optimal emissions performance. Although this increased emissions performance may be within permit levels initially, the emissions rate will continue to deteriorate as contaminants continue to build on compressor blades over time.
Accordingly, it would be desirable to have a cost-effective, portable, self-contained cleaning system for cleaning gas turbine compressors. Additionally, it would be desirable to have a cleaning system and process for rapidly cleaning such turbine compressors while utilizing minimum volumes of water and/or washing fluids.